Improved Analog Costas Loop with Fuzzy Logic Controller

Costas loop is a widely used PLL-based circuit for carrier tracking in modern telecommunication. In this paper, a modification in the classical Costas loop is proposed where voltage-controlled oscillator is incorporated with an additional phase control along with its traditional frequency control. It can be seen that this modification can lock the Costas loop much faster. The simulation result further corroborates the enhancement in the lock-in range of this modified loop. It is also further shown that with the use of fuzzy logic controller (FLC), this modified classical Costas loop again gets locked much faster.